Document: 333D012G
5-18-2007
- 20 -
Decontamination procedure
WARNING
Only qualified technicians should perform this procedure.
1. Surface-disinfect the inside of the window and all other surfaces on the view screen assembly.
2. Multiply the total volume of the cabinet (49, or 78 ft
3
) by .3 gram/ft
3
of space to determine the amount of
paraformaldehyde required to decontaminate the cabinet. If the cabinet is vented to the outside you must
consider the volume of the duct work in the paraformaldehyde calculation.
3. Prior to sealing up the cabinet make sure all gas or flammable petcocks are closed and pressure tight. Use a
soap bubble solution to make sure there is no leakage. Note: You are creating a confined space.
4. The inside cabinet work space should be at room temperature with 60% to 85% relative humidity. If relative
humidity is low (10 to 30%) add a pan of boiling water on the work surface. If it is (40% to 55%) add a pan
of hot tap water on the work surface. Relative humidity above 85% will require extra clean up which will be
covered in step 15. Note: Without the proper relative humidity the formaldehyde gas will not be
effective. The mode of entry of formaldehyde into the living organisms is through the cell wall by the
absorption of water.
5. Place a heating mantle with paraformaldehyde in the work space. The heating mantle must be able to reach
450 degrees F and must have a grounded plug that should be plugged in to an outlet outside the cabinet.
6. This step is optional. Place a second heating mantle in the cabinet with 10% more by weight of ammonium
bicarbonate than paraformaldehyde. This will be used later in step 13 to neutralize the formaldehyde gas.
7. This step is recommended. Place spore strips inside the cabinet to confirm that the decontamination process
has been successful.
8. If the cabinet is vented to the room, use a sheet of plastic and seal the front access and exhaust port openings.
These openings should be sealed such that the exhaust airflow recirculates back to the front access opening.
This will promote the even distribution of formaldehyde gas throughout the cabinet.
9. If the cabinet is vented to the outside, then the exhaust transition should have a means to recirculate the
exhaust airflow back to the cabinet blower. This will promote the even distribution of formaldehyde gas
through the exhaust filter. Seal the front access opening.
10. Turn on the heating mantle containing the paraformaldehyde flakes.
11. After 25% of the paraformaldehyde has depolymerized, turn on the cabinet blower for 10 to 15 seconds.
Repeat after 50%, 75% and 100% of the paraformaldehyde has depolymerized.
12. Allow the formaldehyde gas a minimum residence time of 12 hours, preferably over night.
13. Turn on the heating mantle containing NH4HCO3 and the cabinet blower and allow the two gases to circulate
for at least one hour. Then vent the cabinet to the outside.
14. Aseptically remove spore strip and place in Trypticase-soy broth and incubate for 7 days. No growth will
verify the decontamination process.
15. When cleaning up, you may find residual paraformaldehyde (white powder) on the metal or glass surfaces.
To remove this, use ammonia in warm water, wear gloves and wipe down the affected surfaces. The
paraformaldehyde will dissolve in water and be neutralized by the ammonia.
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